Development of an inexpensive, portable medical nebulizer is proposed for targeted delivery of monodisperse aerosols to the lung. This nebulizer will not use CFCs, will be breath actuated, and will deliver the aerosol at low velocity and high droplet density. These attributes are not present in any single nebulizer currently on the market. The unique technical aspect of the proposed nebulizer is a small (l cm x l cm) silicon chip containing a very large array of extremely small micronozzles from which droplets are dispensed. By using integrated circuit manufacturing techniques, more than 10,000 of these micronozzles will be created on a single chip. These chips will produce very large numbers of microdroplets, each equal in diameter to the micronozzle orifice size, which will vary from 0.5 micromole to greater than 10 micromoles. The proposed nebulizer will not require high pressures, an external pressure source, ultrasonic energy or other extravagant means for droplet creation. Diminution of the bulk liquid into droplets occurs naturally by the Rayleigh instability of the jet formed at each micronozzle. This nebulizer will be effective in delivering medications to patients with asthma, cystic fibrosis, MDS-related pneumocystis carinii pneumonia, bronchitis, emphysema, and other lung-related ailments. PROPOSED COMMERCIAL APPLICATION: The proposed nebulizer will be marketed as a replacement for all existing mechanisms for generating therapeutic and diagnostic aerosols. This includes replacement of the metered dose inhaler, the jet nebulizer, the spinning disk generator and the Sinclair-LaMer aerosol generator.